1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Expection of Angular Momentum

  1. Nov 11, 2009 #1
    1. The problem statement, all variables and given/known data

    I am trying to calculate the expectation of the y-component of the angular momentum L.
    $<L_{y}>$. How should I approach this?


    2. Relevant equations

    I try to write it in terms of the following commutator

    $L(y) = \frac{2*pi}{ih} [L_{x}, L_{z}]$


    3. The attempt at a solution
     
  2. jcsd
  3. Nov 11, 2009 #2

    Avodyne

    User Avatar
    Science Advisor

    What do you know about the state in which you are to take the expectation value?
     
  4. Nov 11, 2009 #3
    Hi there, the state is given as |l, m>, where l is the orbital angular momentum quantum number, and m is the magnetic moment quantum number.

    I want to prove that to compute <l,m| L(y) |l,m> = <L(y)> =0, how should I approach this?

    Many thanks!
     
  5. Nov 11, 2009 #4

    gabbagabbahey

    User Avatar
    Homework Helper
    Gold Member

    If I were you, I'd write [itex]L_y[/itex] in terms of the raising and lowering operators [itex]L_{\pm}[/itex]...
     
  6. Nov 11, 2009 #5
    Hi there, thank you for your reply.
    I was told that I have to use the commutation relation between the L(x) and L^2 to get the expectation value of L(y). How can I do that though?

    Thanks
     
  7. Nov 11, 2009 #6

    gabbagabbahey

    User Avatar
    Homework Helper
    Gold Member

    I'm not sure...the only way I know of showing it is to use the raising and lowering operators.

    You seem to be working on basically the exact same problem as jazznaz in this thread, so maybe you two should work together and see what you can come up with.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Expection of Angular Momentum
Loading...